1. Field of the Invention
The present invention relates to recording liquids (hereinafter referred to as inks) for making records on recording media such as paper, resin films, and the like by using an ink-jet system or a writing tool such as a fountain pen, felt pen, or the like.
2. Description of the Prior Art
An ink-jet recording system comprises forming ink droplets by any of various ink-discharging techniques and causing a portion or all of the droplets to deposit onto a recording medium such as paper or the like, to carry out recording. Inks known and used for the ink-jet recording system are solutions or dispersions of various water-soluble dyes or pigments in vehicles such as water and mixtures of water with water-soluble organic solvents.
Similar inks are also employed for recording with writing tools such as fountain pens, felt pens, and ball pens.
A variety of performance characteristics are naturally required for these inks. The most strongly required characteristic is stability of the liquid against occurrence of deposit that may clog a nozzle or an orifice of a recorder or a pen point during recording or after short-time or long-term intermission. This characteristic is specially important for thermally actuated ink-jet recording system, since temperature changes tend to cause deposition of a foreign matter on the surface of the heating heads. However, inks of prior arts need some additives in order to satisfy various requirements in respect of the conditions of ink discharge, long-term storage stability of inks, distinctness and optical density of recorded images, surface tension and electrical properties of inks, etc. Moreover, the prior art inks involve a number of problems such that the nozzles and orifices of ink-jet recorders may clog, deposits may develop on the surface of the heating heads, and precipitates may appear during long-term storage due to various impurities contained in the used dyes. This is one of the reasons why ink-jet recording systems do not rapidly come into wider use in spite of their many superior features.